JPH0771840B2 - Copper clad laminate and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a copper clad laminate used as a surface mounting printed wiring board for chip components such as resistors and ICs, and a method for producing the same.

2. Description of the Related Art In recent years, electronic components used have rapidly changed from leaded components to chip components due to the trend toward smaller, lighter weight and higher density electronic devices, and the mounting method is mainly surface mounting on printed wiring boards. Is becoming. In this background, printed wiring boards,
That is, the following severe characteristics have been required for the copper clad laminate which is the material.

A general problem when mounting chip components will be described with reference to the explanatory view of FIG. In this case, the thermal expansion coefficient of the chip component 1 and the laminated plate that becomes the substrate 4 (generally, a laminated plate obtained by heat-pressing a prepreg such as glass cloth, glass non-woven fabric, or paper impregnated with a thermosetting resin) If the coefficients of thermal expansion differ greatly,
The solder joint portion 3 connecting the chip component 1 and the copper circuit 2 is cracked by a load such as a thermal cycle, so that it cannot be practically used. The thermal expansion coefficient of commercially available chip components such as ICs and transistors is 2 to 7 × 10 ⁻⁶ / ° C., while the substrate on which the chip components are mounted is the above-mentioned laminated plate,
17 to 20 × 10 ^-6 / ° C. Therefore, a copper clad laminate having a thermal expansion coefficient close to that of the chip component is required.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, the thermal expansion coefficient of a laminated plate obtained by heat-press molding a glass cloth impregnated with the above-mentioned general-purpose thermosetting resin, a glass non-woven fabric, a prepreg such as paper is large, It is difficult to secure reliability. Another requirement is that if the warpage in the solder reflow process when mounting the chip components is not small, it cannot be prevented from falling during temporary adhesion of the chip components or it cannot be applied to an automatic assembly line. The copper-clad laminate was not fully satisfactory in terms of suppressing warpage. As a device for satisfying the above requirements, it is conceivable that the substrate 4 shown in FIG. 2 is a ceramic plate having excellent dimensional stability and a small coefficient of thermal expansion, but it cannot be drilled, is easily cracked, and has a large size. However, it is not suitable for automatic mounting of chip components because it has the drawbacks of being difficult and expensive to use.

The present invention has improved the above-mentioned conventional drawbacks, and has (1) excellent surface mounting reliability of chip parts, (2) small warpage even during solder reflow in the mounting process, and printed wiring from a copper clad laminate An object of the present invention is to provide a copper clad laminate for a printed wiring board, which is suitable for mounting chip components, and which has a small warpage in the step of processing the board and can be processed by the same method as the conventional copper clad laminate.

Means for Solving the Problems That is, the present invention, a copper foil is integrated on one side or both sides of a laminate formed under heat and pressure a layer of prepreg impregnated with a thermosetting resin sheet-shaped substrate In the copper-clad laminated plate, as shown in FIG. 1, the laminated plate 5 and the copper foil 8 are
However, the synthetic resin layer 6 and the laminate 5 which are more flexible than the laminate 5
The thermosetting resin layer 7 having a smaller coefficient of thermal expansion is integrated in this order from the laminated plate 5 side.

In addition, in contrast to the above specified invention, the merged invention is a copper clad laminate in which a copper foil is placed on one or both sides of a layer of a prepreg in which a sheet-shaped base material is impregnated with a thermosetting resin and is molded under heat and pressure. In manufacturing the plate, between the prepreg layer and the copper foil,
A synthetic resin layer that is more flexible than the cured laminate of the prepreg layer, and a thermosetting resin layer having a thermal expansion coefficient after curing smaller than that of the laminate are interposed in this order from the prepreg layer side, and heated and pressed. It is to be integrally molded into.

Action The present invention has the above-mentioned characteristics, and when a copper clad laminate is subjected to etching processing by a conventional method to form a printed wiring board, and the chip component 1 is mounted and soldered as shown in FIG. Due to the effect of the thermosetting resin layer 7 having a small coefficient, even if a thermal cycle load is applied, stress concentration does not occur in the solder joint portion 3 and cracks do not occur, and reliability can be secured.

Further, the synthetic resin layer 6 serves as a cushioning material by interposing the synthetic resin layer 6 between the laminated plate 5 having a large thermal expansion coefficient and the thermosetting resin layer 7 having a small thermal expansion coefficient, and the thermosetting resin layer 7 is laminated. It is possible to solve problems such as increase in thermal expansion under heating load, cracks or delamination at the interface without being affected by the plate 5, and in particular, it acts as a stress relaxation layer.

EXAMPLES In carrying out the present invention, the laminate is an epoxy resin-glass cloth, an epoxy resin-glass nonwoven fabric laminate, a polyimide resin-glass fabric, a polyimide resin-glass nonwoven fabric laminate, a phenol resin-paper laminate, or the like. is there. Further, the thermosetting resin layer having a small coefficient of thermal expansion can be appropriately selected depending on the laminated plates to be combined, but the epoxy resin used for the laminated plate, the polyimide resin, the inorganic filler in the phenol resin, that is, SiO ₂ , MgO, A cured layer of a mixed composition filled with powder of AI ₂ O ₃ or the like, or a cured layer of a prepreg obtained by impregnating and coating the composition on a glass cloth, a glass nonwoven cloth, a polyimide / amide fiber cloth, etc. having a small thermal expansion coefficient. . The thickness and resin content of the thermosetting resin layer and the content of the inorganic filler can be selected so as to be as close as possible to the thermal expansion coefficient of the chip component, but the adhesiveness with the copper foil, the printed wiring board processing It is necessary to consider the workability at the time.

Further, the synthetic resin layer is more flexible than the laminated board in order to exert the effect as a stress relaxation layer, that is, a resin layer having a low Tg point, preferably a temperature of 100 which is normally set in a printed wiring board processing step or the like. Desirably below ℃. Further, this thickness can be selected in consideration of the thermosetting resin layer, the type of laminate, the workability as a copper clad laminate, the electrical characteristics, and the like. Examples of materials used include polyvinyl butyral modified phenolic resin,
Examples thereof include polybutadiene-modified epoxy resin. still,
The resin layer may be formed by applying this resin to paper, Tetoron cloth, glass non-woven cloth, glass cloth or the like.

As a specific example of the manufacturing method, first, a prepreg obtained by impregnating a base material such as glass cloth or glass non-woven cloth or paper with a thermosetting resin varnish and drying the prepreg is prepared. SiO ₂ to the thermosetting resin varnish, varnish mixed with an inorganic filler such as Al ₂ O ₃ is applied to a copper foil and dried to form a thermosetting resin layer, or a thin glass nonwoven fabric is applied and dried. And make it a prepreg,
Intervene during molding. One side of one ply of the prepreg manufactured above is coated with a flexible synthetic resin layer, for example, polyvinyl butyral-modified phenol resin, and dried. Then, a plurality of prepregs manufactured in step 1 are stacked, and one ply is stacked with the synthetic resin layer of the prepreg manufactured in step 1 above, and the prepreg manufactured in step 3 is stacked to place a copper foil, or A copper foil provided with a thermosetting resin layer is placed.

It is possible to adopt a method in which the components thus stacked are sandwiched between mirror surface plates and heated and pressed by a press to form a copper clad laminate.

Example 1 Dicyandiamide as a curing agent and acetone as a solvent were added to a bisphenol type epoxy resin to prepare an epoxy resin varnish, and the varnish was applied to a glass cloth and dried to obtain a resin amount.
A 40% epoxy resin-glass cloth prepreg having a thickness of 0.2 m / m was prepared.

70% as solid weight% in the epoxy resin used above
% Silica powder (SiO ₂ ) and methyl ethyl ketone,
The varnish obtained by mixing and stirring was applied to a 35 μ thick electrolytic copper foil and dried to prepare a copper foil having a thermosetting resin layer having a thickness of 80 μ.

The epoxy resin-glass cloth prepreg 1 ply produced above was taken, and a varnish prepared by dissolving a polybutadiene-modified epoxy resin in acetone was applied to one surface of the prepreg using a roll coater, and dried to give a synthetic resin layer having a thickness of 80 μ on one surface. Prepared a prepreg with mochi.

Six plies of the epoxy resin-glass cloth prepreg prepared above were stacked, then one ply of the prepreg prepared in step 1 was stacked with the synthetic resin layer on top, and the copper foil prepared in step 2 was stacked with the thermosetting resin layer down. It was placed on the resin layer.

This composition is sandwiched between two mirror-faced plates, inserted into a press, heated and pressed at a temperature of 160 ° C and a pressure of 80 kg / cm ^{2 for} 60 minutes, then cooled and then a single-sided copper-clad laminate with a thickness of 1.6 m / m. Got

The properties of the single-sided copper-clad laminate are shown in Table 1. The thermal expansion coefficient (α) of the laminate pressed only with the epoxy resin-glass cloth prepreg is 18 × 10 ^-6 / ° C, the Tg point is 120 ° C,
Further, in the layer obtained by curing only the epoxy resin containing the inorganic filler, α was 11 × 10 ⁻⁶ / ° C. and Tg point was 130 ° C. Further, the Tg point of a cured product of only the synthetic resin layer = polybutadiene-modified epoxy resin was 80 ° C.

Example 2 135 g of paulownia oil-modified phenolic resin varnish for general-purpose laminated boards
A kraft paper of / m ² was impregnated and dried to prepare a phenol resin-paper prepreg having a resin amount of 50%.

The epoxy resin used in Example 1 as solid weight%
60% SiO ₂ and Al ₂ O ₃ mixed inorganic filler (trade name Satinton, made by Tsuchiya Kaolin) and methyl ethyl ketone were added and mixed and stirred, and the resulting varnish was applied to 35μ thick electrolytic copper foil and dried. A copper foil having a thermosetting resin layer with a thickness of 50 μm was prepared.

80% polyvinyl butyral modified phenolic resin varnish
A prepreg to be a synthetic resin layer having a thickness of 90 μm was prepared by impregnating a g / m ² linter paper and drying it.

Phenol resin-paper prepreg prepared above 6
A ply was laminated, and a prepreg to be a synthetic resin layer adjusted on both sides was laminated on each ply, and copper foil prepared on both sides was laminated under the same conditions as in Example 1 to obtain 1.6 m / m. A thick double-sided copper clad laminate was obtained.

The characteristics of the double-sided copper-clad laminate are shown in Table 1. In addition, the coefficient of thermal expansion (α) of the laminated board pressed only with the phenol resin-paper prepreg is 21 × 10 ⁻⁶ / ° C., the Tg point is 80 ° C., and a cured layer containing only an epoxy resin containing an inorganic filler. Was 13 × 10 ^-6 ℃, Tg point was 125 ℃. Further, the Tg point of the cured product of only the synthetic resin layer = polyvinyl butyral modified phenol resin was 40 ° C.

Comparative Example 1 Epoxy resin-glass cloth prepreg prepared in the section of Example 1 was overlaid on 8 plies, 35 μm thick copper foil without adhesive was placed and pressed under the same molding conditions as in Example 1 to obtain 1.6 m / An m-thick single-sided copper-clad laminate was obtained. The properties of the copper clad laminate are shown in Table 1.

Comparative Example 2 Eight plies of the phenol resin-paper prepreg prepared in the section of Example 2 were overlaid, 35 μm thick copper foil with adhesive was overlaid on both sides, and pressed under the same molding conditions as in Example 2 to 1.6 m / A double-sided copper clad laminate having a thickness of m was obtained. The properties of the copper clad laminate are shown in Table 1.

EFFECTS OF THE INVENTION As described above, according to the present invention, the structure thereof is provided on the surface of the laminated plate with a synthetic resin layer which is more flexible than the laminated plate,
Furthermore, since the copper foil is integrated on the surface of the laminate with a thermosetting resin layer having a smaller thermal expansion coefficient than the laminated plate,
As shown in Table 1, it was possible to obtain a copper clad laminate having a small amount of warpage in the printed wiring board process and the solder reflow process and having excellent surface mounting reliability of the intended chip component. Further, since the thermosetting resin layer and the synthetic resin layer as described above are provided on the lower side of the copper foil, the water absorption rate is lowered and the solder resistance is improved.

[Brief description of drawings]

FIG. 1 is a sectional explanatory view showing an example of a copper clad laminate of the present invention,
FIG. 2 is a cross-sectional explanatory view when a chip component is mounted as a printed wiring board using a conventional copper clad laminate. 5 is a laminated plate, 6 is a synthetic resin layer, 7 is a thermosetting resin layer, 8
Is copper foil.

Claims (8)

[Claims] 1. A copper-clad laminate in which a copper foil is integrated on one side or both sides of a laminate obtained by molding a layer of a prepreg in which a sheet-shaped base material is impregnated with a thermosetting resin under heat and pressure,
The laminated board and the copper foil are integrated by interposing a synthetic resin layer having flexibility more than the laminated board and a thermosetting resin layer having a smaller thermal expansion coefficient than the laminated board in this order from the laminated board side. Characteristic copper clad laminate. 2. The thermosetting resin layer having a small coefficient of thermal expansion is an inorganic filler-containing thermosetting resin layer.
The copper clad laminate according to the item. 3. A copper clad laminate is produced by placing a copper foil on one or both sides of a layer of a prepreg impregnated with a thermosetting resin on a sheet-like substrate and molding under heat and pressure to produce a copper clad laminate. Between the prepreg layer and the copper foil, a synthetic resin layer that is more flexible than the laminated plate in which the prepreg layer is cured, and a thermosetting resin layer having a thermal expansion coefficient after curing smaller than the laminated plate from the prepreg layer side. A method of manufacturing a copper-clad laminate, which comprises interposing in this order and integrally molding under heat and pressure. 4. The thermosetting resin layer having a small coefficient of thermal expansion is an inorganic filler-containing thermosetting resin layer.
A method for producing a copper clad laminate according to the item. 5. The method for producing a copper clad laminate according to claim 3 or 4, wherein the flexible synthetic resin layer is formed by previously coating the surface of the prepreg layer with the resin. . 6. The copper clad laminate according to claim 3 or 4, wherein the flexible synthetic resin layer is obtained by previously impregnating a sheet-shaped base material with the resin and interposing the resin during molding. Manufacturing method. 7. The copper clad laminate according to claim 3 or 4, wherein the thermosetting resin layer having a small coefficient of thermal expansion is formed by previously coating the resin on the back surface of the metal foil. Manufacturing method. 8. The thermosetting resin layer having a small thermal expansion coefficient is obtained by impregnating a sheet-shaped base material with the resin in advance and interposing the resin during molding. Laminated board manufacturing method.